Circuit breakers are known which include a piston for blasting the arc, with the piston-operating energy being obtained, at least in part, from the gas whose pressure increases due to the increase in temperature produced by the arc. One such conduit breaker is described in French Pat. No. 77 19086.
Proposals have been made to further increase the pressure to which the piston is subjected by equipping the circuit breaker with a set of electrodes for forming a second arc which is established at the same time as the first.
One such circuit breaker is described, for example, in U.S. Pat. No. 3,985,988.
However, it has been observed that such a circuit breaker suffers from drawbacks.
By multiplying the number of arc zones, there is an increased risk of an arc restriking after a circuit-breaking operation. In particular the second arc is not of any use for interrupting low currents, in particular low inductive currents.
An object of the invention is to provide a circuit breaker including an arc-blasting piston and in which a second arc for increasing the force exerted on the piston is established solely when the current to be interrupted is high (short circuit element, for example), with said auxiliary arc not being established when the current to be interrupted is low (inductive current, no-load circuit breaking).